Popular Science Monthly/Volume 15/July 1879/A Question of Eating
|A QUESTION OF EATING.|
IT has long been considered, as by common consent a law of health, that all food should be eaten slowly, not swallowed until well masticated.
Some observations and experiments, however, have been recently made which indicate strongly that this principle of slow eating, so far as health is concerned, is not true with respect to all varieties of food.
Animals in a state of nature, as is generally recognized, tend to accommodate themselves in the most favorable manner to their conditions: if a cow naturally ruminates, why should a dog naturally take a chunk of meat at a swallow without stopping to chew it? It may be said that the ruminant has a special digestive apparatus, but the fact remains that the food is eaten as is best suited to it, and the dog, following nature, does what is best for him, or, in other words, if it disagreed with his digestion to eat rapidly, he would reform, and take it more slowly. Following out this idea, experiments were made upon a dog, with the following results: It the meat, before being fed to the dog, was reduced to a hash, or cut into fine pieces, the digestion was at best imperfect, a considerable portion of the undigested or imperfectly digested meat being found in the excreta. If, under the same conditions, meat was fed to the dog in large pieces, it was bolted at a gulp, with the result that little, if any, passed through undigested; compared with the result from the chopped meat, it could be called a perfect digestion for the coarse form, as compared with a decidedly imperfect digestion for the fine form. So far as simple experiment goes, this must be pretty conclusive for the dog; but can the same hold true with respect to the human subject?
A brief review of the first portion of the digestive process, so far as understood with regard to man, will help in answering this; and first to be considered is the mouth and chewing apparatus. Says Foster: "The chief purpose served by the saliva in digestion is to moisten the food, and so assist in mastication and deglutition. . . . In man, it has a specific solvent action on some of the food-stuffs. On fats it has only a slight emulsifying action, and on proteids none. Its characteristic property is that of converting starch into grape-sugar." According to Wundt, "the mouth secretions possess, besides mechanical, chiefly a chemical action—the changing over of the starch and glycogen contained in the food into sugar. The ferment body, which produces this transformation, ptyaline, is not a specific element of the mouth-secretion, since, aside from the intestinal secretions, all tissues and fluids of the body contain starch-ferment."
From this it will be seen that no digestive action on meat or animal food takes place before reaching the stomach, and that, for vegetable food even, the action of the mouth-secretions is far from all-important.
As to the mechanical action of the mouth in preparing the food for deglutition, this is not specially necessary for morsels of meat of the ordinary size introduced into the mouth, while for a large portion of the vegetable or plant products eaten—and it is upon these that the saliva exerts its chemical action—mastication is necessary before they can be swallowed. The meat-foods are in themselves sufficiently moist, while many dried fruits, breads, and the like, in endless variety, first need thorough reduction.
A piece of jelly the size of a walnut would give little trouble in swallowing, since it is moist and of a yielding character, while few can swallow a pill the size of a pea without distress. Teeth and chewing, then, have their purpose, but, with the exception of the incisors occasionally, that purpose does not include meat unless it has become dried; this is with respect to the food before it reaches the stomach, but, of course, the question then arises, Would it not be in a better condition for digestion if it had been thoroughly masticated?
The food on reaching the stomach is kept in rotary motion by the muscular walls, and only after a time does it begin to pass the pyloric orifice, and then only by degrees, since the digestion farther on is a much finer operation, and can go on but slowly. The length of time that the digestion properly takes, is, according to the present knowledge of the subject, several hours—in fact, somewhat longer than has generally been supposed. Now, if the meat is swallowed fine cut, it begins to pass through very quickly, and before it has been fully acted upon by the gastric juice. This action as regards meats consists in "dissolving the sarcolemma from the muscular fibers, and in dissolving proteid matters and converting them into peptones. . . . On starch, gastric juice has per se no effect whatever. . . . On grape-sugar and cane-sugar healthy gastric juice has no effect." In fats alone it has a slight emulsifying effect, but if still in the tissue it is dissolved out. Milk is accordingly acted on by being first curdled on reaching the stomach, after which it is leisurely dissolved again in the desired form.
The rotary movement of the contents of the stomach is to facilitate the action of the gastric juice—to bring the various particles and lumps of the entire mass into contact with it as it exudes from the stomach's walls. If the material has come from the mouth finely ground up, a considerable portion goes over into the duodenum before it has been properly acted upon; but, if it has come down in coarse lumps, these begin shortly to dissolve, passing into a more or less fluid condition, and this can be taken care of with about the same rapidity by the digestive apparatus following: by this arrangement no portion of the food would be allowed to pass from the stomach unprepared for the next step in the digestive process. All portions, then, even the finest fibers, of a meat diet, must be acted upon by the gastric juice before passing on; and this action progresses best by slowly wearing off the outside of the morsels.
Professor Ludwig has made some general experiments as to the truth of this theory upon himself, eating coarsely-cut meat at one time and fine at another, without at least being able to detect any ill effects whatever from morsels as large as it was convenient to swallow. Many workingmen, business men, and others, almost bolt their food without loss of excellent digestion; we should bear in mind, of course, that they have to chew much of their vegetable food for convenience in swallowing, and also that the indigestion of business men occasionally is due more to their nervous condition at the time.
A slight amount of chewing or mumbling serves to detect harsh substances, as bones, and to prepare for swallowing; foreign matters of considerable size will, however, gradually make their way, and, if not rough, may pass without injury. The writer once had an experience of this nature with a piece of iron an inch in length and a third in diameter.
To conclude, then, with respect to man as well as other flesh-eaters: it is not only not necessary, but also not best, to chew meat of any kind to a fine condition, but to swallow it in convenient morsels; this militates against hash. With regard to all non-meat food, careful mastication is better, but hardly so necessary as has been supposed.
- "Text-book of Philosophy," M. Foster, 1877.
- "Lehrbuch der Physiologie des Menschen," W. Wundt, vierte Auflage, 1878.
- Lectures of Professor C. Ludwig (Leipsic), 1878-'79.